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Effectiveness of Bleaching Agents Used in the Walking Bleach Technique

Explore the potential of walking bleaching for nonvital teeth through a systematic review and clinical cases

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PURCHASE COURSE
This course was published in the November/December 2023 issue and expires December 2026. The authors have no commercial conflicts of interest to disclose. This 2 credit hour self-study activity is electronically mediated.

AGD Subject Code: 780

Educational ­Objectives

After reading this course, the participant should be able to:

  1. Define nonvital tooth discoloration and treatment options.
  2. Explain the methodologies used in a systematic review related to the effectiveness of the walking bleach technique.
  3. Evaluate the prognosis of walking bleach techniques and various bleaching agents based on recent evidence.

Achieving an esthetically pleasing smile heavily relies on the color of the teeth, which significantly impacts a patient’s appearance and mental well-being.1,2 Patient expectations often extend be­yond simply addressing the shade of a tooth in need of prosthodontic restoration.3

Bleaching has emerged as a viable alternative to crowning for anterior teeth that have undergone endodontic treatment.4 Restorative procedures involved in placing full-coverage restorations can negatively impact patients’ oral health. Although crowns are often the most appropriate treatment choice, the placement of a full-coverage restoration for a discolored tooth in an attempt to provide a predictable and permanent solution may not always result in a favorable long-term outcome.5

Tooth discoloration is either intrinsic or extrinsic. While extrinsic discoloration can be caused by chlorhexidine mouthrinses, stannous fluoride exposure, and iron supplements, intrinsic causes are pulp hemorrhage, pulp deterioration, microorganisms and their byproducts, tetracycline, pulp necrosis, intracanal medications, some endodontic filling materials, and metallic restorations.1

Several approaches exist for treating discolored teeth. These vary from invasive methods, such as crowns, veneers, and direct restorations, to less invasive procedures, including macroabrasion, microabrasion, and bleaching. Additionally, dental prophylaxis is a simple treatment option.6 The approach to treating discolored teeth differs between vital teeth and those undergoing endodontic treatment. The cause of discoloration and potential underlying infections must be considered before deciding on treatment.7

For nonvital teeth, intracoronal whitening is a minimally invasive treatment option. During intracavity bleaching, the bleaching agent acts directly on the dentin structure.8 Stained teeth are treated with hydrogen peroxide, carbamide peroxide, or sodium perborate gels, all of which contain hydrogen peroxide as the active ingredient that whitens the teeth through an oxidation chemical reaction.9

The walking bleach technique, thermocatalytic technique, and in-office methods can all be used to bleach endodontically treated teeth. In the walking bleach technique, proper root filling and establishment of a cervical seal are crucial. The bleaching agent should be changed every three to seven days. The walking bleach approach often uses a lower concentration of hydrogen peroxide to minimize potential changes to the histological and morphological features of the tooth structure.7

Considering the available evidence-based literature on the prognosis of walking bleach techniques with different whitening agents, this systematic review aims to evaluate the prognosis of the technique itself and the various whitening agents used in the walking bleach technique.

Methodology of the Systematic Review

The major databases, including Pubmed/MEDLINE and Science Direct, were searched for the past 5 years including randomized control trials, cohorts, and in vitro studies, which showed 92 results. A Boolean search was conducted, and the following keywords were used: “bleaching,” “teeth bleaching,” “walking bleach,” “walking bleaching,” “office bleaching,” “sodium perborate,” “hydrogen peroxide,” “internal bleach,” “nonvital teeth,” and “non-vital teeth.”

Our study team carried out the literature retrieval and evaluation. The articles were evaluated independently by all researchers for the studies to converge on the area of interest, and articles with incomplete information in the title or abstract were excluded. The reviewers examined titles and abstracts, and related articles were selected by title only in the first step; 43 relevant papers were found. In the second stage, irrelevant articles were eliminated based on their abstracts first and then their full content; this left 14 papers. Researchers then identified the relevant articles by reviewing the full content of the remaining articles in the list, excluding in-vitro and systematic review studies, which showed eight results pertinent to the subject.

Two cases were also reported by the researchers and the following considerations have been included in the paper: potential risks and complications of internal bleaching, the proper case selection for the bleaching treatment, patient’s and dentist’s esthetic expectations, and different agents available for delivering the bleaching treatment.

Results of the Systematic Review

A total of 184 patients with an initial number of 194 endodontically treated teeth were included in all articles. Of these, 172 endodontically treated teeth received bleaching as treatment, with 69 treated with hydrogen peroxide, 101 treated with carbamide peroxide, and two treated with sodium perborate. The mean patient age was 30.54 years with the youngest being 18 and the oldest being 65.1,10 The average follow-up period was 12 months. However, some studies had longer follow-up periods, with one study tracking participants for up to 25 years, while others had shorter periods, such as immediate assessment after bleaching. Most participants were women, however, the percentage of female participants varied across the studies. Hydrogen peroxide (five studies) and carbamide peroxide (four studies) were the most commonly used agents for tooth bleaching among our studies.

In all reviewed studies, a clinically significant difference was reported after delivering the bleaching treatment in all individuals regardless of the whitening agent, their treatment protocols, and assigned groups. However, in the randomized clinical trials, no significant difference was reported between the two groups.9

Most studies with a follow-up period of less than 2 years reported satisfactory results using their respective bleaching techniques. However, in a contrasting long-term study, Amato et al10 reported six failures out of 40 samples over a 25-year period, resulting in the recurrence of tooth discoloration.

The definition of success varied across the studies. The term used as the clinically significant difference was determined based on the tooth shade change, patient satisfaction, and researcher satisfaction after the bleaching treatment.

Clinical Case 1

A 48-year-old woman complained about discoloration of her right upper central incisor (Figure 1). We did not note any significant dentin loss in the cervical portion, extensive restorations, or visible cracks (Figure 2). The patient was given the option of internal bleaching after evaluating the tooth both radiographically and clinically (Figure 3).

FIGURE 1. Initial appearance of the smile. Evidence of discoloration of the right upper central incisor.
FIGURE 2. Initial peria¬pical radio¬graph. Absence of periapical lesion and satisfactory endodontic treatment.

For the bleaching protocol on tooth #8 we used a mixture of sodium perborate and articaine. During the first visit, we removed the composite from the lingual aspect and filled the access until the cementoenamel junction (CEJ) with a glass-ionomer restorative material. Next, we placed a mixture of sodium perborate and articaine in the chamber and covered it with the glass-ionomer material before light-curing it. We made necessary adjustments to the occlusion, and we scheduled a follow-up appointment for evaluation after 1 week.

FIGURE 3. Pulp chamber accessed from palatal.
FIGURE 4. Final photo after the second visit. No difference was noted in the third visit as well.

On the second visit, we observed that the incisal edge had whitened, while the cervical portion had not. Therefore, we removed the glass-ionomer material from the lingual aspect and introduced a new dose of articaine into the pulp chamber. We then covered the bleach with the glass-ionomer material and light-cured it. We took intraoral photos and asked the patient to come back in 1 week for re-evaluation.

During the third visit, the patient and the clinician were dissatisfied with the results. We discussed the complications of applying the internal bleach agent again and offered alternative treatment options such as the preparation of a new crown or veneer (Figure 4).

Clinical Case 2

A 63-year-old nonsmoking woman complained about discoloration of her right upper central incisor (Figure 5). On our examination, we did not note any significant dentin loss in the cervical portion, extensive restorations, or visible cracks. The patient was given the option of internal bleaching as a treatment after evaluating the tooth both radiographically and clinically (Figure 6). For the bleaching protocol on tooth #8, we used a mixture of sodium perborate and articaine. During the first visit, we removed the composite from the lingual aspect and filled the access until the CEJ with glass-ionomer restorative. Next, we placed a mixture of sodium perborate and articaine in the chamber and covered it with glass-ionomer material before light-curing it. We scheduled a follow-up appointment for evaluation after 1 week.

FIGURE 5. Initial appearance of the smile. Evidence of discoloration of the right upper central incisor
FIGURE 6. Initial periapical radiograph. Absence of periapical lesion and satisfactory endodontic treatment.

On the second visit, we observed that the gray discoloration on the buccal surface of tooth #8 was no longer visible, but yellow discoloration remained. We placed a new mixture of sodium perborate and articaine in the canal and closed its access with glass-ionomer restorative. We scheduled a follow-up appointment for re-evaluation after 1 week.

FIGURE 7. Third visit: the discoloration had lightened to a light-yellow shade

During the third visit, we observed that the discoloration had lightened to a light-yellow shade. The patient expressed satisfaction with the shade change, and we scheduled veneer preparation and possible gingivectomy for the next appointment as the patient was not completely satisfied with the final esthetic outcome (Figure 7).

Discussion

The results of our study demonstrated that walking bleaching generally produces satisfactory outcomes in most patients, regardless of the whitening agent and protocol used. These findings align with a systematic review conducted by Frank et al,11 which analyzed eight studies up to 2022. To ensure the inclusion of recent advancements in bleaching agents and techniques, we focused on studies published from 2017 on including two case reports by our researchers. Due to significant variations and high heterogeneity among the studies, a meta-analysis was not performed.

The studies revealed varying degrees of shade change after completion of walking bleach treatment, indicating a clinically significant difference before and after treatment. However, shade change doesn’t necessarily reflect patient satisfaction. Interestingly, our clinical reports didn’t align with the results obtained from the reviewed papers.

In the first case, the patient expressed complete dissatisfaction, while in the second case, although the patient was satisfied with the shade change, her ultimate esthetic expectations were not fully met. Consequently, we did not record her satisfaction with the outcome and proceeded with alternative treatment through veneer preparation.

The case reports, including ours, showcased the use of different whitening agents with varying concentrations, as well as diverse application protocols in terms of treatment duration and switching intervals for fresh bleaching agents. From the analysis of these reports, the treatments’ success rates do not significantly differ when comparing different whitening agents with varying concentrations.

When managing discolored teeth, clinicians have several treatment options and combinations at their disposal.5 Factors, such as safety and effectiveness, play vital roles in the clinician’s decision-making process.12 After reviewing eight articles, it became evident that while different etiologic factors, including pulp necrosis, infection, trauma, and endo sealer, do not significantly affect the outcome of walking bleach treatment, other facets can impact the final result. For instance, walking bleaching tends to yield better outcomes in younger patients compared to elderly patients.7,13 In the case of older adults, the natural aging process leads to the deposition of secondary dentin, affecting the light-transmitting properties of teeth, resulting in gradual darkening.7 Furthermore, certain root canal sealer materials are less likely to whiten with internal bleaching; however, bleaching can still reduce the intensity of the grayish color.14

While a significant difference cannot be definitively linked to patient satisfaction, a closer examination of the studies revealed that dissatisfaction with the outcome is more common in necrotic teeth and those with discoloration caused by root canal treatment sealer materials compared to other discolored teeth. Most of the patients in our studies were women but no significant difference was observed between the sexes.15

Various investigators have conducted follow-ups ranging from 3 days to 25 years. Amato et al10 conducted a 25-year follow-up study with a success rate of 85%, demonstrating that nonvital bleaching can be considered a long-lasting treatment for whitening tooth discoloration. While other studies and case reports have included follow-ups, longer follow-up periods would be helpful in future case reports.

Significant flaws existed in the reviewed articles as well. One major drawback of all published articles is the absence of a suggested protocol for maintaining the bleaching effect after treatment. We recommend investigating the effectiveness of specific toothpastes and toothbrushes in sustaining the outcomes of walking bleaching. Moreover, in the study conducted by Knezevic et al,13 confusion exists regarding the final study sample size, making it difficult to ascertain the exact number of studied teeth and patients.

Although we documented clinically significant differences among most studies and patients, these differences alone do not determine the success of the treatment. The definition of success may vary between clinicians and patients, as demonstrated by our two case reports. The predictability of the walking bleach result is not completely assured, and it is crucial to consider the expectations of patients. Additionally, the effectiveness and success rate of nonvital bleaching can vary depending on the etiological cause of tooth discoloration.

Conclusion

Our study confirmed that walking bleach tends to yield satisfactory results in most patients, regardless of the bleaching agent and protocol used. The findings were consistent with previous research, although our clinical reports showed discrepancies. Shade change does not necessarily indicate patient satisfaction. The success rates of whitening agents with varying concentrations did not significantly differ. Factors such as age, tooth condition, and root canal sealer materials can influence the outcomes of walking bleaching. Longer follow-up periods and the development of protocols for maintaining the bleaching effect are recommended. Ultimately, understanding patient expectations and considering the underlying causes of tooth discoloration are essential to achieving successful outcomes in nonvital bleaching treatments.


References

  1. Bersezio C, Ledezma P, Estay J, Mayer C, Rivera O, Fernández E. Color regression and maintenance effect of intracoronal whitening on the quality of life: rct—a one-year follow-up study. Oper Dent. 2019;44:24–33.
  2. Machado AC, Braga SRM, Ferreira D, Jacintho FF, Scaramucci T, Sobral MAP. Bleaching of severely darkened nonvital tooth case report — 48 months clinical control. J Esthet Restor Dent. 2021;33:314–322.
  3. Kahler B. Present status and future directions – managing discoloured teeth. Int Endod J. 2022;55:922–950.
  4. Shillingburg HT, Sather DA, Wilson EL, et al. Fundamentals of Fixed Prosthodontics. 3rd ed. Chicago: Quintessence Publishing; 2014.
  5. Poyser NJ, Kelleher MGD, Briggs PFA. Managing discoloured non-vital teeth: the inside/​outside bleaching technique. Dent Update. 2004;31:204–214.
  6. Joshi SB. An overview of vital teeth bleaching. Journal of Interdisciplinary Dentistry. 2016;6(1):3-13.
  7. Plotino G, Buono L, Grande NM, Pameijer CH, Somma F. Nonvital tooth bleaching: a review of the literature and clinical procedures. J Endod. 2008;34:394–407.
  8. Georgieva I. Intracavity tooth bleaching in the aesthetic zone of maxilla using carbamide peroxide gel — case report. Journal of IMAB. 2020;26(3):3223–3225.
  9. Bersezio C, Vildósola P, Sáez M, et al. Does the use of a “walking bleaching” technique increase bone resorption markers? Oper Dent. 2018;43:250–260.
  10. Amato A, Caggiano M, Pantaleo G, Amato M. In-office and walking bleach dental treatments on endodontically-treated teeth: 25 years follow-up. Minerva Stomatol. 2018;67:225–230.
  11. Frank AC, Kanzow P, Rödig T, Wiegand A. Comparison of the bleaching efficacy of different agents used for internal bleaching: a systematic review and meta-analysis. J Endod. 2022;48:171–178.
  12. Reitzer F, Ehlinger C, Minoux M. A modified inside/​outside bleaching technique for nonvital discolored teeth: a case report. Quintessence Int. 2019;50:802–807.
  13. Knezevic N, Obradovic M, Dolic O, et al. Clinical testing of walking bleach, in-office, and combined bleaching of endodontically treated teeth. Medicina (B Aires). 2022;59:18.
  14. Yang WC, Tsai LY, Hsu YH, Teng NC, Yang JC, Hsieh SC. Tooth discoloration and the effects of internal bleaching on the novel endodontic filling material SavDen® MTA. J Formos Med Assoc. 2021;120(1 Pt 2):476–482.
  15. Watts A, Addy M. Tooth discolouration and staining: a review of the literature. Br Dent J. 2001;190:309–316.

From Decisions in Dentistry.November/December 2023; 9(10):36-41

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